Apparatus for lining kilns

ABSTRACT

Apparatus for installing adjacent rings of bricks against a cylindrical wall, such as a kiln shell, characterized by a wheel mounted frame, a main conveyor at the bottom of same for moving bricks longitudinally, a transverse group forming conveyor disposed at each side of the main conveyor, a swingable arm for each group forming conveyor having clamping apparatus for grasping a group, and a swingable operator platform for each clamping apparatus from which the movement of a group is controlled to its desired position in the ring. Certain parts of the apparatus which are disposed in the upper two quadrants, when in use, are foldable into the lower two quadrants to facilitate installation of the apparatus through an end aperture of a kiln having a cross section less than the kiln cross section and which also renders the apparatus more compact for transportation over roads to its various loci of use. In use, the kiln remains stationary and the bricks are retained by gravity in the lower two quadrants. After they reach the horizontal diameter they are retained in place in the upper two quadrants by suitable supports and until they are finally keyed together at the tops of the upper quadrants.

iinite States Newman atent 91 [54] APPARATUS FOR LINING KILNS [76] Inventor: Vance W. Newman, 15442 Turner Road, Victorville, Calif. 92392 [22] Filed: Apr. 22, 1971 [21] Appl No.1 136,409

[52] US. Cl .52/749, 52/747 [51] int. (:1. ..]E04g 21/14, E04g 23/02 [58] Field of Search ..S2/747, 749',

[56] References Cited UNITED STATES PATENTS Primary Examiner-Frank L. Abbott Assistant Examiner-Carl D. Friedman Attorney-Sheridan, Ross & Burton 5 7] ABSTRACT Apparatus for installing adjacent rings of bricks against a cylindrical wall, such as a kiln shell, characterized by a wheel mounted frame, a main conveyor at the bottom of same for moving bricks longitudinally, a transverse group forming conveyor disposed at each side of the main conveyor, a swingable arm for each group forming conveyor having clamping apparatus for grasping a group, and a swingable operator platform for each clamping apparatus from which the movement of a group is controlled to its desired position in the ring. Certain parts of the apparatus which are disposed in the upper two quadrants, when in use, are foldable into the lower two quadrants to facilitate installation of the apparatus through an end aperture of a kiln having across section less than the kiln cross section and which also renders the apparatus more compact for transportation over roads to its various loci of use. In use, the kiln remains stationary and the bricks are retained by gravity in the lower two quadrants. After they reach the horizontal diameter they are retained in place in the upper two quadrants by suitable supports and until they are finally keyed together at the tops of the upper quadrants.

10 Claims, 14 Drawing Figures PATENIEB MAY 2 91973 SHEEI10F4 INVENTOR VANCE W. NEWMAN ATTORNEYS PATENIEUWZWQYFI 3; 735,546

SHEET 2 BF 4 PATENTEU m2 9 I975 SHEET 3 OF 4 APPARATUS FOR LINING KILNS BACKGROUND OF THE INVENTION In the manufacture of Portland cement it is common practice to feed raw materials, such as limestone, clay, and various additives into the upper end of a cylindrical kiln mounted for rotation on a slightly downwardly inclined axis and into which flame is projected from the lower discharge end. Since the discharge end is subjected to the greater temperature, maximum erosion of the tire brick lining occurs in this locus which requires replacement at certain intervals. Thus, in a kiln of say feet diameter and 500-600 feet in length, about 30-100 feet of lining adjacent the discharge end must be periodically replaced. The down time of a kiln of this size may result in a loss of the order of $20,000/day. It becomes apparent, accordingly, that it is highly important, for economic reasons, to effect the repair in a minimum of time. Also, in the original installation of the lining to the entire length of the kiln, the labor costs for same becomes important and the reduction of installation time may effect considerable savings in the initial cost of the kiln.

Two general procedures are employed in the installation of such brick. In the first, brick is installed in the lower half of the kiln shell, that is, to approximately the horizontal diameter of same, after which the semicircular ring is suitably secured and the kiln rotated 180. Bricks are then installed in the now lower half to complete the ring, after which key brick are finally installed to secure the ring within the shell. In the second procedure referred to, the brick are installed in the lower two quadrants as in the first procedure, but the shell is not rotated. Brick are then installed upwardly around the upper two quadrants, retaining same in place with suitable supporting apparatus, and key brick are finally installed at the top between the upper tw quadrants.

SUMMARY OF THE INVENTION The present invention employs the general procedure of that last referred to. A mobile frame or vehicle is disposed within the kiln and locked to same in a position to install a ring or course of bricks. The frame carries two elevatable operator platforms from which an operator in each controls installation of brick through 180 of a vertical diameter. The bricks are fed longitudinally along a conveyor disposed adjacent the bottom of the vehicle and are transferred laterally in opposite directions until two groups of bricks, such as six, are formed. Each group is picked up by a swingable clamp which transfers the group to the desired locus. When the clamp is released, a pusher plate engages the group and moves it longitudinally into place and in engagement with an original or completed new ring of bricks. When the horizontal diameter is reached, the bricks in the upper two quadrants are pushed between the shell and holding devices which are then radially moved to force and maintain the group in desired position. When the upper two quadrants have been nearly completed, key brick of selected sizes are hand laid on a similar support and suitable wedge plates are driven between the key bricks to complete the ring.

To reduce the overall size of the apparatus to facilitate transportation over roads and the like, and also to render it insertable within an end of a kiln having a size less than the internal cross section of the kiln, certain parts of the apparatus are constructed to fold and reduce its cross sectional size. For example, jacking masts, the operator platforms, and the upper quadrant holding devices all fold into the lower quadrants whereby the apparatus, when folded, fits within the lower two quadrants of the kiln cross section.

One of the objects of the invention, accordingly, is to provide apparatus for lining kilns and the like which is operated by two operators, each of which controls the installation at each side of a vertical diameter of the kiln.

Another object is to provide a conveyor which assembles a plurality of bricks into groups for each operator, which are formed during the interval between picking up a group and returning for the next group.

Another object is to provide novel apparatus for clamping a group and swinging it to a desired position in a partial ring and transferring it to the top of same.

Another object is to construct the apparatus with foldable parts to reduce its size when not in use.

Another object is to provide novel brick supports for holding the brick against the shell during the formation of the upper two quadrants of a ring.

7 Afurther object is to provide a novel brick support for the key bricks installed between the upper quadrants.

Still further objects, advantages and salient features will become more apparent from the description to follow, the appended claims, and the accompanying drawmg.

' BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation of the subject of the invention, portions being omitted and others shown somewhat diagrammatically;

FIG. 2 is an end elevation of FIG. 1;

FIG. 3 is a side elevation, portions being shown in section, of a clamping device illustrated more diagrammatically in FIGS. 1 and 2;

FIG. 4 is a radially outward elevation as viewed in the direction of arrow 4, FIG. 3;

FIG. 5 is an elevation as viewed in the direction of arrow 5, FIGS. 3 and 4;

FIG. 6 is a side elevation, portions being broken away, of a main conveyor and transfer apparatus to a pair of group assembly stations;

FIG. 6a is a like view in another position of parts;

FIG. 7 is a diagrammatic elevation as viewed in the direction of arrow 7, FIG. 6;

FIG. 8 diagrammatically illustrates a synchronous drive mechanism for parts of FIGS. 6, 6a and 7;

FIG. 9 is an end elevation of a key brick holding device;

FIG. 10 is a section taken on line 10-10, FIG. 9;

FIG. 11 is a detail of a portion of FIG. 1 at the locus of arrow 11;

FIG. 12 is a detail of an elevator operating mechanism; and

FIG. 13 is a detail of a portion of a brick carrier arm and its operating mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT General Description Referring now to the drawings, and particularly FIGS. 1 and 2, all relatively fixed parts of the apparatus comprise a frame 20, the parts of which may be formed of suitable structural shapes, rigidly secured together by welding, suitable fastenings, or the like. The rear end of the frame is supported by a pair of angularly spaced wheels 22, 24, preferably provided with resilient tires, such as pneumatic. The front end of the frame is similarly supported by a pair of adjacent like wheels 26 which are disposed centrally between and forwardly of the rear wheels. Wheels 26 thus may roll along shell S of kiln K adjacent its lowermost portion (6 oclock) and wheels 22, 24 may roll along bricks B along oppositely angularly spaced points from the lowermost portion of the shell. A suitable power drive (not shown) is preferably carried by the frame which may be selectively coupled to certain of the wheels, such as 22 or 24, or both, for advancing the apparatus longitudinally along the kiln. An engine or electric motor (not shown) may be selectively coupled to conveyor mechanism for forming groups of bricks, to be subsequently described in detail, and also drives a hydraulic pump for operating various hydraulic rams. Rear mast 28 is provided with a hydraulic cylinder 30 which operates a ram 32 and front mast 28a is provided with a like bydraulic cylinder 30a and ram 32a. An adjustable stop or foot 34 is provided adjacent each of the rear wheels and a like stop or foot 36 is provided to engage shell S at 6 o'clock adjacent front wheels 26. As shown in FIG. 1, stops 34 and 36 have been adjusted to prevent compression of the various tires and rams 32, 32a have been elevated, forming a rigid three point support for frame 20 at its lower portions and urged downwardly at 12 oclock by the longitudinally spaced masts. The frame is now rigidly and immovably affixed to the kiln and in position to apply a ring of bricks to the shell adjacent an existing ring of bricks or adjacent a ring just previously applied.

An arm 38 is pivotally secured to the frame at its longitudinal central axis for swinging movement from near 6 oclock upwardly in the third and fourth quadrants and a like arm 380, a portion of which is shown, is similarly secured to the frame for upward swinging movement from near 6 oclock in the second and first quadrants. Each arrn is swung between desired positions by an actuator 40, such as a double acting hydraulic cylinder and ram, pivoted at one end to arm 38 and at its other end to the frame.

An operator elevator 42 is secured to the frame by parallelogram linkage 44 which may be swung upwardly by a hydraulic actuator 46. A like elevator (not shown) is similarly secured to the frame for movement in the other two quadrants. The control (not shown) for the various instrumentalities are carried by the elevators and an operator in each controls the application of the bricks in his two quadrants.

Arms 38, 38a are each provided with a radially extensible portion 48, slideably mounted therein and operated by a double acting hydraulic actuator 50. The outer end of each extensible portion carries a clamping device 52 which grasps a group of bricks adjacent 6 oclock and carries same to proper position to be deposited in the ring of bricks being formed. The bricks are assembled into groups at assembly stations 54, 54a adjacent 6 o'clock which receive the bricks from a main conveyor 56. The clamping devices 52, which form important components of the invention, and the assembly forming stations, will now be described in greater detail.

Clamping Devices Referring, now, to FIGS. 3 to 5, the radially extensible end 48 of arm 38 (or like end-of arm 38a) is provided with a pair of parallel tubular guides 60 which slideably receive guide rods 62 aflixed to clamp frame or carrier 64. A double acting hydraulic cylinder 66 is aflixed to end 48 and is provided with a ram 68, one end of which is affixed to carrier 64. As will be apparent, operation of cylinder 66 controls rectilinear movement of carrier 64 in opposite longitudinal directions of the apparatus. A C clamp 70 is pivotally connected by a pin 72 to the carrier and limit stops 74 are preferably provided to limit its pivotal movement so that it is floatably carried by the carrier for limited angular rotation about pin 72. A hydraulic cylinder 76, having a ram or jaw 78, is carried by one arm of the C-clamp, the other arm terminating in a stationary jaw. As be apparent, when a group of bricks are disposed between the jaws and the movable jaw is moved to clamping position the group may be bodily carried by the clamping device between a group forming station to a desired position in the ring of bricks being formed. It will be apparent, however, that when the group of bricks is elevated to a desired position to form a continuation of the ring being formed, the jaws of the C-clamp must be disposed ahead of and clearing such ring. A pusher plate 80, operated by hydraulic actuators 82 is therefore provided which forces the group longitudinally rearwardly and out of the jaws when the group has been elevated to the desired angular position just ahead of the ring being formed. Also, to reduce the distance which the pusher plate is moved, the C-clamp jaws engage the end of the group adjacent their forward portions, rather than centrally, which would require a greater stripping distance across the C-clamp jaws. Actuators 82 have been illustrated as of the single acting type with a spring return but, as will be understood, they may be of the double acting type, if desired.

Main Conveyor and Group Assembly Stations While the groups of bricks could be manually assembled at stations 54, 54a, preferably this is attained in more rapid and less labor consuming manner to now be described. Referring, now, to FIGS. 6 to 8, main conveyor 56 comprises a downwardly inclined frame 84 which rotatably carries a plurality of parallel idler rolls 86 on which bricks B may roll by gravity feed. A frame 88, having like idler rolls 90, forms an extension of the main conveyor and is pivoted for vertical movement about a pivot pin 92, fixed relative to the vehicle frame. A fixed position stop 94 extends above rolls 90, and as will be apparent, when a brick rolls from main conveyor 56 onto extension conveyor 88 its motion is arrested by the stop, as shown in FIG. 6. An eccentric 96 periodically and pivotally elevates conveyor 88 which, as shown in FIG. 6a, has moved to a position in which the first roll 90 thereon has blocked further movement of the foremost brick on conveyor 56. At the same time, this elevation of conveyor 88 permits a brick on conveyor 88 to roll across stop 94 and against a fixed stop 98. Referring now to FIG. 7, a pivotally mounted paddle 100, operated by a crank and pitrnan 102, is disposed adjacent the lower terminal end of conveyor 88 and swings in a direction transverse to its longitudinal direction. When the paddle moves from the full line position to the dotted position it will transfer brick B from against stop 98 laterally onto assembly station 54a, which comprises a set of idler rolls 104 rotatably carried by an arcuate fixed frame (not shown). As the brick passes onto the laterally disposed assembly station it rolls across a pivoted lever 105, similar to a ratchet, which prevents its retrograde motion. When the paddle starts to return to its original full line position, eccentric 96 will have rotated to permit the next brick to be disposed against stop 98 and hence return motionof paddle 160 will wipe the next brick onto opposite lateral group forming station 54. As illustrated in FIG. 8, any suitable common drive mechanism may be employed to operate the eccentric and paddle in synchronism so that each one-half oscillation of the paddle transfers a brick to one or the other of group forming stations 54, 54a. When both stations are full, such as having six bricks on each, any suitable sensing control, which detects this condition, may be employed to discontinue operation of the eccentric and paddle until a new demand is required on assembly stations 54, 54a.

General Operation If it be assumed that the group forming stations are disposed in the same plane as the ring to be formed, as shown in FIG. 1, and the ring is about to be formed, clamping device 52 may be lowered and radially contracted to grasp the first group of bricks disposed on a group assembly station. It may then be swung upwardly, extended, and returned to its original angular position and the group laid on the shell beneath the assembly station. The next group is then removed from an assembly station by aligning the C-clamp 70 with such group and moving it rearwardly to grasp the group, after which it is swung upwardly to the desired position and the group pushed rearwardly from the clamp by pusher plate 80.

Formation of Top Quadrants After the ring is formed in the lower two quadrants, or slightly therebeyond, special brick holding apparatus is then required until the ring is keyed in place at its uppermost portion (12 oclock). For this purpose arcuate frames 1 (FIG. 2) are provided in the first and fourth quadrants. Each frame supports a plurality of arcuate members 1 12 having spring urged plungers 114 therein (like those illustrated in FIG. 10), each arcuate member 112 being radially movable by rods 117, affixed thereto, disposed in guides 119, under control of a hydraulic actuator 116. The placement of a group of bricks into the ring being formed is similar to that previously described except that an arcuate member 112 is now disposed in spaced relation adjacent the inner periphery of the group, forming an arcuate annular space between it and the shell. A group of bricks is swung to a position in alignment with the arcuate annular space just referred to and just ahead of same. The group is then moved longitudinally into such space but since the jaws of clamp 70 cannot move into such space, the group is now spaced from the adjacent completed ring by the longitudinal thickness of the jaws. Hydraulic actuator 116 then forces member 112 radially outwardly so that plungers 114 resiliently force the bricks against the shell. Clamping jaw 78 is then released and pusher plate 80 is actuated which slides the bricks across plungers 114 and into contact with the adjacent ring previously formed. This operation continues upwardly in the first and fourth quadrants until about one group spacing remains adjacent 12 oclock.

Completion of the Ring Referring to FIGS. 9 and 10, a holding device 118 is disposed on a bar 120, extending between the masts (see FIG. 1), this device comprising an arcuate member 122, like 112 previously described, having resiliently urged plungers 114 and operated by a hydraulic actuator 124. Member 122 is preferably connected to the actuator by a pivot pin 126 to provide limited angular float. The last group of bricks (which may individually vary in width) are selected to fit the keying space above plungers 114 and suitable shims are then driven between the bricks to compact the ring into tight engagement with the kiln shell. All holding devices in the upper two quadrants may then be released.

Adjustments and Collapsible Features Referring again to FIG. 1, when front wheels 26 reach the existing bricks in the kiln they may be raised by a suitable screw 128 so that they roll along same, rather than along the shell.

Masts 23, 23a are pivotally connected to the main frame by pivot pins 130 and may be locked thereat by suitable bolts (not shown). When unlocked, they may be folded downwardly, as indicated by the adjacent arrows so that they occupy positions 180 from that shown, thus materially decreasing the vertical height of the apparatus.

As shown in FIGS. 2 and 11, each arcuate frame 110 is provided with a shaft support 132, vertically journaled in a member 134 affixed to a shaft 135 by a pivot 136 and bolt 137, shaft 135 being joumaled to frame 20 for rotation about a horizontal axis. Bolt 137 provides limited angular adjustment of shaft 132 about the axis of pivot 136. A removable strap clamp 138 locks shaft 132 to the main frame in the position shown in FIG. 11 wherein each arcuate frame is now rigidly secured in the operative position of FIG. 2. When it is desired to fold an arcuate frame 110 into stowed position, clamp 138 is removed and arcuate frame 110 is rotated about the vertical and horizontal axes to a position in which its plane is disposed adjacent the central portion of the main frame. As will be apparent, the other arcuate frame folds to stowed position in like manner.

As best shown in FIG. 12, each elevator is pivotally connected to main frame 20 by a post 140 joumaled for rotation about a vertical axis. Parallelogram links 44 are pivotally connected to the post and to an elevator support 142 which supports the operator compartment 42. The compartment is preferably pivoted to the elevator support about a vertical axis 144 disposed eccentrically from the center of the compartment so that it has oscillatory movement relative thereto to facilitate moving the compartment to various positions within the space available. Hydraulic cylinder 46 is bodily carried by the post and swings with same about the axis of post 141).

As shown in FIG. 2, rear wheels 22, 24 are rotatable about fixed intersecting axes, the planes of the wheels being disposed in radial planes. Preferably, however,

the axes of rotation are adjustable so that the planes of the wheels may be disposed in parallel relation, when desired, which reduces the overall height of the apparatus to some extent. Further, they are preferably steerable to more readily position the apparatus along a desired line of travel as the apparatus is periodically positioned in the kiln after completion of a ring or rings of bricks.

As so far described, it has been assumed that stations 54, 54a are disposed in the plane of the ring being formed and that each time a ring is completed the apparatus must be moved to form the next ring. Actually, however, by providing sufficient rectilinear movement of clamp 70, two rings may be formed between the periodic repositioning of the apparatus along the kiln. Thus, during the time required to key in the top bricks of a ring, which requires manual operations, the elevator operators are proceeding to install bricks in the lower quadrants of the next ring. When keying is completed the apparatus is then moved since members 112 must be repositioned before bricks can be installed in the upper quadrants of the new ring which has been in the process of being formed. As will be apparent, no loss of time by the elevator operators is entailed during the manual keying operation of the previous ring. A horizontal platform (not shown) is disposed rearwardly of and adjacent mast 28 upon which one or more operators stand during the manual keying operation.

As shown in FIG. 2, the upper end of actuator 40 is pivoted to arm 38 about a fixed pivot point thereon. FIG. 13 illustrates a construction in which arm 38 is provided with an arcuate plate 146 which slideably carries a block 14 8 which is pivoted to actuator 40. In the operation of this mechanism block 148 remains in the fiill line position until arm 38 swings to about a horizontal position. Upon further upward movement, block 148 slides to the other end of plate 146, as shown by the dotted position. This provides a longer lever arm from the pivot point of arm 38 as the arm moves further upwardly which provides a more sensitive control over the movement of the arm.

What is claimed is:

1. Apparatus for installing adjacent rings of bricks, to the inner surface of a cylindrical wall having a central longitudinal axis, such as a kiln shell, said wall forming lower and upper pairs of quadrants, comprising:

a. a main frame movable longitudinally within said wall and means for securing same thereto at spaced positions therealong,

b. brick assembly stations for supporting two groups of juxtaposed bricks adjacent the bottom of the wall, one at each side of a vertical diameter thereof,

c. a radially extensible arm for each group pivoted to the frame for swinging movement substantially about said longitudinal axis,

d. a clamp device carried by the outer end of each arm for releasibly grasping one of said groups,

e. means for moving each clamp device relative to an arm in the longitudinal direction of the wall,

f. upper brick support means disposed within the upper pair of quadrants for temporarily holding the blocks in position therein and until they are finally keyed between the upper pair of quadrants, and

g. a control station for each arm for controlling the angular extent of its swinging movement, its radial extension, the longitudinal movement of a clamping device, and the clamping and release thereof.

2. Apparatus in accordance with claim 1 wherein the control station for each arm comprises a pair of operator elevators swingable substantially about said longitudinal axis, whereby an operator carried by each may observe and control installation of blocks in his respective upper and lower quadrants.

3. Apparatus in accordance with claim 2 wherein each elevator includes a platform on which an operator may stand, and means for maintaining same in a sub stantially horizontal position in all positions of its swinging movement.

4. Apparatus in accordance with claim 1 wherein each clamping device is constructed to engage opposite ends of a group closely adjacent the forward faces thereof, and a movable pusher member associated therewith engageable with said forward faces for moving the group rearwardly out of engagement with the clamping device.

5. Apparatus in accordance with claim 4 wherein each clamping device includes a U-shaped flame, the bight portion of which is pivotally connected to its carrying arm to permit limited angular float, whereby all of the blocks of a group may be forced into engagement with the wall.

6. Apparatus in accordance with claim 1 wherein the means for forming the two groups of bricks comprises a central main conveyor for carrying all of the bricks, and means for alternately moving the bricks from the main conveyor to form said groups.

7. Apparatus in accordance with claim 6 wherein the main conveyor includes spaced idler rolls on which the bricks may descend by gravity, a pivoted continuation of said main conveyor adapted to receive one brick and thence pivot upwardly to block entry of the next brick thereto, said brick assembly stations each having arcuately disposed idler rolls, an oscillatable paddle operated in synchronism with the pivoted motion of said continuation, operable to alternately transfer a brick on said continuation to one or the other of said brick assembly stations.

8. Apparatus in accordance with claim 7 including means associated with each brick assembly station for permitting delivery of a brick thereto but preventing downward retrograde motion of the bricks as they are assembled thereon.

9. Apparatus in accordance with claim 1 wherein said main frame rotatably carries a pair of wheels adjacent its rear end adapted to roll along previously installed bricks, the wheels being disposed at opposite sides of the vertical diameter of the wall, and at least one wheel rotatably carried by the front end of the frame adapted to roll along the cylindrical wall at a locus adjacent the lowermost portion thereof, thus forming a three-point wheeled support, an upwardly extending extensible mast adjacent each end of the frame, and abutrnents carried by lower portions of the frame, the construction being such that when the masts are extended they, and the abutrnents, rigidly afiix the frame to the wall and inactivate rolling action of the wheels.

10. Apparatus in accordance with claim 1 including a pair of upwardly extending extensible masts pivotally carried by the flame, said upper support means being pivoted to the frame, the construction being such that when the masts and upper support means are pivoted downwardly they fit within the space of the lower quadrants. 

1. Apparatus for installing adjacent rings oF bricks, to the inner surface of a cylindrical wall having a central longitudinal axis, such as a kiln shell, said wall forming lower and upper pairs of quadrants, comprising: a. a main frame movable longitudinally within said wall and means for securing same thereto at spaced positions therealong, b. brick assembly stations for supporting two groups of juxtaposed bricks adjacent the bottom of the wall, one at each side of a vertical diameter thereof, c. a radially extensible arm for each group pivoted to the frame for swinging movement substantially about said longitudinal axis, d. a clamp device carried by the outer end of each arm for releasibly grasping one of said groups, e. means for moving each clamp device relative to an arm in the longitudinal direction of the wall, f. upper brick support means disposed within the upper pair of quadrants for temporarily holding the blocks in position therein and until they are finally keyed between the upper pair of quadrants, and g. a control station for each arm for controlling the angular extent of its swinging movement, its radial extension, the longitudinal movement of a clamping device, and the clamping and release thereof.
 2. Apparatus in accordance with claim 1 wherein the control station for each arm comprises a pair of operator elevators swingable substantially about said longitudinal axis, whereby an operator carried by each may observe and control installation of blocks in his respective upper and lower quadrants.
 3. Apparatus in accordance with claim 2 wherein each elevator includes a platform on which an operator may stand, and means for maintaining same in a substantially horizontal position in all positions of its swinging movement.
 4. Apparatus in accordance with claim 1 wherein each clamping device is constructed to engage opposite ends of a group closely adjacent the forward faces thereof, and a movable pusher member associated therewith engageable with said forward faces for moving the group rearwardly out of engagement with the clamping device.
 5. Apparatus in accordance with claim 4 wherein each clamping device includes a U-shaped frame, the bight portion of which is pivotally connected to its carrying arm to permit limited angular float, whereby all of the blocks of a group may be forced into engagement with the wall.
 6. Apparatus in accordance with claim 1 wherein the means for forming the two groups of bricks comprises a central main conveyor for carrying all of the bricks, and means for alternately moving the bricks from the main conveyor to form said groups.
 7. Apparatus in accordance with claim 6 wherein the main conveyor includes spaced idler rolls on which the bricks may descend by gravity, a pivoted continuation of said main conveyor adapted to receive one brick and thence pivot upwardly to block entry of the next brick thereto, said brick assembly stations each having arcuately disposed idler rolls, an oscillatable paddle operated in synchronism with the pivoted motion of said continuation, operable to alternately transfer a brick on said continuation to one or the other of said brick assembly stations.
 8. Apparatus in accordance with claim 7 including means associated with each brick assembly station for permitting delivery of a brick thereto but preventing downward retrograde motion of the bricks as they are assembled thereon.
 9. Apparatus in accordance with claim 1 wherein said main frame rotatably carries a pair of wheels adjacent its rear end adapted to roll along previously installed bricks, the wheels being disposed at opposite sides of the vertical diameter of the wall, and at least one wheel rotatably carried by the front end of the frame adapted to roll along the cylindrical wall at a locus adjacent the lowermost portion thereof, thus forming a three-point wheeled support, an upwardly extending extensible mast adjacent each end of the frame, and abutments carried by lower portions of the frame, the construction being such that when the mAsts are extended they, and the abutments, rigidly affix the frame to the wall and inactivate rolling action of the wheels.
 10. Apparatus in accordance with claim 1 including a pair of upwardly extending extensible masts pivotally carried by the frame, said upper support means being pivoted to the frame, the construction being such that when the masts and upper support means are pivoted downwardly they fit within the space of the lower quadrants. 